1. Field of the Invention
The present invention relates to a device for forming an electrostatic latent image for use in electrostatic recording and, in particular, to an electrostatic latent image forming device using ion stream control.
2. Description of the Related Art
Conventionally, there has been known an electrostatic latent image forming device of the above-mentioned type, which will be described below. As shown in FIG. 23, in the conventional electrostatic latent image forming device, drive electrode 101 are disposed on an insulating base plate 100 in such a manner that the drive electrodes are parallel to one another. Control electrode 104 are disposed above the drive electrodes through an insulating layer 102 in such a manner that the control electrodes 104 cross over the drive electrodes 101 respectively. The drive electrode 101 and the control electrodes 104 cooperate to form a matrix. Also, each of the control electrode 104 includes two long and narrow electrodes 105 and 105 disposed in parallel to each other, so as to form a space area 106 for generating ions. Further, a flat-plate shaped screen electrode 108 is disposed over the control electrodes 104 through an insulating layer 107. In the screen electrode 108, as shown in FIG. 24, there are formed circular openings 109 for leading ions only at the positions that correspond to the space areas 106 of the control electrodes 104. In this figure, reference numeral 110 designates an opening formed in the insulating layer 107.
The electrostatic latent image forming device applies a high-frequency high voltage across the drive electrodes and control electrode 104, an ion control voltage to the control electrode 104, and a d.c. voltage to the screen electrode 108, as shown in FIG. 24. As a result of this, a creeping corona discharge is generated in the space areas 106 between the drive electrode 101 and control electrode 104, to produce ions. The ions are then accelerated or absorbed by an electric field produced by the control and screen electrodes 104 and 108 to thereby control the release of ions, so that an electrostatic latent image can be formed.
Now, the electrostatic latent image forming device can be installed to a main body of an ion stream control recording device in the following manner. The electrostatic latent image forming device is installed in such a manner that the lower surface of the insulating base plate 100 having the drive electrode 101, control electrodes 104 and the like thereon rests on a holder mount 111, as shown in FIG. 25. The holder mount 111 is disposed on the upper portion of a dielectric drum 112 in such a manner that it is divided into two, namely, right and left sections, and includes an upper surface 111a which is formed in a horizontal surface. The lower surface of the insulating base plate 100 rests on the horizontally formed, upper surface 111a of the holder mount 111.
In the electrostatic latent image forming device, due to the fact that the surface of the insulating base plate 100 on which the drive electrodes 101, control electrodes 104 and the like are provided is located on the lower side of the insulating base plate 100, that is, on the side of the holder mount 111, a feeder terminal for applying a high voltage to the drive electrodes 101, control electrodes 104, and the like is disposed in a space S between the holder mount 111 and dielectric drum 112.
However, the conventional electrostatic latent image forming device has the following problems. The space S formed between the holder mount 111 and dielectric drum 112 is small and thus the feeder terminal for feeding electricity to the drive electrodes 101, control electrodes 104, and the like must be be small enough to fit within the small space S. As such, it is difficult to provide and mount the feeder terminal in the small space S. Also, because the feeder terminal must be provided in the small space S between the holder mount 111 and dielectric drum 112, it is difficult to obtain a positive contact between the feeder terminal and the feeding part of the electrode. It is also hard to provide a positive connection of a necessary high voltage input. Likewise, since the feeder terminal and other components can come near or contact each other, or the feeder terminal can incur a poor contact, there is a possibility that leakage, attenuation or abnormal discharge may occur in the feeder terminal and other components.
In order to solve the above-mentioned problems, some measures can be taken. Specifically, as shown in FIG. 26, the end portions of the drive electrodes 101 and control electrodes 104 may be extended along the surface of the insulating base plate 100 and in the width direction of the base plate 100, and the lower surfaces of the extended portions 101' and 104' of the drive electrodes 101, and control electrodes 104 may be supported by an insulating frame member 113. Further, the portion of the insulating base plate 100 on which the insulating frame member 113 is put may be placed on the holder mount 111, and contact probes 114 may be pressed against the extended portions 101' and 104' of the drive electrodes 101 and control electrodes 104 from above, thereby providing connection of a high voltage input.
In this case, however, the drive electrodes 101 and control electrodes 104 must be extended to provide the extended portions 101', and 104', and also these extended portions 101' and 104' must be supported by the insulating frame member 113, with the result that the electrostatic latent image forming device is complicated in structure and increased in size. As a result, the whole device becomes large-sized and the cost of the device increases.